Speaker
Description
First Name: Theodosios
Last Name: Chatzistergos
Email Address: chatzistergos@mps.mpg.de
Affiliation: Max Planck Institute for Solar System Research, Göttingen, Germany
All Authors: Theodosios Chatzistergos
Abstract: Because direct measurements of solar irradiance exist only from the late 1970s onward, models are required to reconstruct earlier irradiance variations. On timescales from a day and longer, irradiance variations arise due to the evolution of the solar surface magnetic field, manifesting as dark sunspots and bright faculae and network. Accurate irradiance modelling therefore depends on reliable information about the distribution, and temporal evolution of surface magnetic features. Full-disc magnetograms from instruments such as KPVT, SoHO/MDI, and SDO/HMI provide direct measurements of the surface magnetic field since the 1970s, which is roughly the same period that direct measurements of irradiance exist. Ca II K archives can be used to produce unsigned magnetograms back to 1892, while reconstructions over earlier periods infer the solar magnetic field from sunspot or cosmogenic isotope data. Each of these datasets requires its own set of modelling assumptions, and different models handle these assumptions in different ways, leading to substantial discrepancies in their inferred secular trends. In this talk, I will provide an overview of the main approaches used to model solar irradiance and highlight recent advances.